LINCOLN — The state Department of Environmental Management has fined the town $1,000 for what it says is the town’s failure to maintain the decades-old Lime Rock Dam and for not developing an overall repair-and-replacement program for the dam.

Town Administrator T. Joseph Almond said the town will appeal the fine because it has been working for the last two years on developing exactly that type of plan.

The dam, located about a half mile into the woods off Wilbur Road, is not in danger of giving way, DEM Supervising Engineer David E. Chopy said.

“I don’t want people to freak out,” he said.

But he added it has problems that, if not addressed, will get worse over time.

Almond said the town has been working on the dam. In 2006 a four-foot wide corrugated metal spillway pipe was installed near the base of the dam to let water drain from its reservoir, thus easing pressure on it. The town has also cut vegetation from the dam, built a road to it and monitors it at regular intervals and after significant rainfall.

Though it is not in danger of collapse, Chopy said the Lime Rock Dam has been classified as unsafe. It has tree stumps in its embankment, there are areas of erosion and water seeping out at the base of the downstream face and the edges of the four-foot-wide spillway pipe are bent in and susceptible to being blocked by debris.

Trees and other roots in earthen dams like Lime Rock are a particular concern because the plants they anchor can be blown over, Chopy said, and the roots could rip out part of the dam. The trees could also die, and once their roots decay, water could flow through the holes left behind and weaken it.

The dam is a relic of the town’s mill era, holding back a reservoir that was used to provide waterpower for downstream mills. About 150 feet across and around 15 feet high, the earthen dam was built sometime in the early 1900s. The DEM has classified it as a high-hazard dam because, if it were to give way, it would cause a “probable loss of human life.”

A high-hazard designation doesn’t mean the dam will collapse any time soon, Chopy said, just that if it were to happen, it would be destructive. Because of the stumps, seepage and blockage concerns, it is also classified as unsafe.

Chopy said the DEM wants the town to establish specific plans and timetables for repairing and maintaining the dam so that it will no longer be classified as unsafe.

The notice of violation that announced the $1,000 fine ordered that the town reinforce the streambed under the spot where the main spillway pipe lets water out from the dam, so it will not erode and undermine the dam; and that the town submit to the DEM a plan of replacement or repair that the agency can review, critique and approve. The town would then be expected to begin work on the dam once that plan was authorized by the DEM.

Almond said he was surprised by the fine, saying the town had been proceeding with engineering studies of how to replace the dam and had been telling DEM employees about the progress. He said the last written communication the town got from the DEM about the dam was in October 2006, when the agency issued an order that work be finished on the new spillway. Since then, Almond said, the town has had several in-person meetings with DEM engineers and sent reports to the agency, with no indication that the DEM was considering a fine.

The town has spent about $200,000 trying to determine what to do about the dam, which it took responsibility for in 1968, Almond said. A $125,000 study by Pare Engineering suggested three alternatives: rebuild the dam, lower it or remove it. The town has authorized a $75,000 contract to determine what each of those methods would cost.

The most efficient — and expensive — of the options is to reduce the height of the dam, Almond said. The town was seeking state and federal agencies that might help finance the work, which could cost as much as $3 million. He said other options might be cheaper but require similar work 20 or more years from now.

Almond said if the DEM was going to treat the dam situation as an enforcement action, the town would ask the agency to waive some of its wetlands and other regulations to speed up the work. He estimated that if the town went through all the permit application processes the DEM says are required for the replacement of the dam, it could add $1 million and two years or more to the job.

jhill@projo.com